In order to achieve success in the game of bowling, it is necessary to release the ball in a manner such that it is engaged in two types of motion.
The first motion, "roll", is a rotation of the ball about its horizontal axis, which propels it down the alley toward the pins. The second motion, "spin", is a rotation of the ball about its vertical axis. The manner in which the pins scatter after being struck is dictated largely by the "roll" and "spin" combination imparted to the ball.
Some bowlers experience great difficulty in achieving an effective combination of these two motions. Too much spin may cause the ball to strike the pins too far off center or may even cause the ball to veer off the alley before it reaches the pins. Too little spin may be ineffective in achieving the desired scattering of the pins. Too much or too little roll may, respectively, overwhelm or be overwhelmed by the spin motion.
Experimentation by those skilled in the game has shown that reinforcing the wrist, hand and fingers of the bowler and limiting their relative movement during release aids in attaining an ideal combination of spin and roll. Of particular importance is maintaining the wrist and forefinger at a steady angle throughout delivery and release of the ball.
A number of prior art devices have been unsuccessful in achieving a consistent, effective combination of the roll and spin motions. Only of the best, the device of U.S. Pat. No. 4,371,163, successfully limits the movement of both the wrist and the forefinger. But a significant drawback of that device is that the angle at which the wrist is held may not be adjusted. The most comfortable wrist angle varies from bowler to bowler. Furthermore, different combinations of spin and roll may be achieved by varying the angle at which the wrist is held. Through experimentation, a bowler can determine his ideal wrist angle in terms of both comfort and effectiveness. Limitation of the wrist to one particular angle may impose a corresponding limitation on the bowler's game, as the bowler may be much more effective with his wrist held at another angle.